Vane air motor with prevention of leaking radial bearing grease

ABSTRACT

A vane air motor is disclosed which is configured to prevent grease in a radial bearing from leaking into a rotor chamber. The vane air motor has a motor housing ( 20 ) having a rotor chamber, a rotor ( 22 ) with vanes ( 24 ) disposed in the rotor chamber, a first end wall ( 16 ) of the motor housing equipped with a radial bearing ( 50 ) rotatably supporting a support shaft portion ( 28 ) of the rotor, and a casing contiguously joined to the motor housing to form a compressed air supply chamber ( 44 ) together with the first end wall to supply compressed air into the rotor chamber through an air supply hole ( 46 ) formed in the first end wall. The first end wall has communication means ( 16 - 5, 16 - 6  and  16 - 7 ) for supplying compressed air from the compressed air supply chamber to the side of the first radial bearing closer to the rotor.

RELATED APPLICATIONS

This application is a continuation of PCT/JP2010/050019 filed on Jan. 5,2010, which claims priority to Japanese Application No. 2009-002306filed on Jan. 8, 2009. The entire contents of these applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vane air motor usable as drivingmeans for pneumatic grinders and so forth.

2. Description of the Related Art

Conventionally, a vane air motor has a motor housing having a circularcylindrical inner peripheral surface defining a rotor chamber in themotor housing and a rotor eccentrically and rotatably installed in themotor housing and having vanes. The rotor has an output shaft portionprojecting from one end surface of the rotor along the axis of rotationof the rotor. The output shaft portion is rotatably supported by an endwall of the motor housing. The rotor further has a support shaft portionprojecting from the other end surface of the rotor in coaxial relationto the output shaft portion. The support shaft portion is rotatablysupported by another end wall of the motor housing. The vane air motorfurther has a governor having a shaft-shaped rotating member coaxiallysecured to the support shaft portion to rotate together with the supportshaft portion. When the shaft-shaped rotating member is rotated at anumber of revolutions greater than a predetermined one, the governorlimits a compressed air supply flow path supplying compressed air intothe rotor chamber to suppress the number of revolutions of the rotor.

The output shaft portion and the support shaft portion are supported byradial bearings provided in the end walls, respectively, of the housing.The radial bearings comprise inner races secured to the output andsupport shaft portions, respectively, outer races provided radiallyoutward of the respective inner races, and spherical or circularcylindrical rolling members provided between respective combinations ofinner and outer races.

The motor housing and the governor are enclosed by a casing of apneumatic grinder or the like to which the vane air motor is attached,and compressed air to be supplied into the rotor chamber is suppliedthrough a compressed air supply chamber formed around the governor bythe casing and through an air supply hole formed in the motor housing(Patent Literature 1 noted below).

Patent Literature: Patent Literature 1: Japanese Patent ApplicationPublication No. 2001-9695

In the vane air motor having the above-described structure, the pressurein the compressed air supply chamber, in which the governor is disposed,is higher than in the rotor chamber in which the rotor is disposed. Therotor chamber and the compressed air supply chamber are divided fromeach other by the end wall of the motor housing which end wall receivesthe support shaft portion of the rotor extending therethrough andsupports it by means of the radial bearing. Therefore, the above-noteddifference in pressure causes grease in the radial bearing to graduallyleak into the rotor chamber. Grease entering the rotor chamber adheresto vane end portions near the above-described end wall. Because of itshigh viscosity, the grease hinders smooth radial movement of the bladesrelative to the rotor. However, such does not occur at the radialbearing in the other end wall of the motor housing, and no greaseadheres to vane end portions near the other end wall. Consequently, eachblade is inclined between one end and the other end thereof. For thisreason, the distal edge of each vane is pressed against the cylindricalwall surface with a stronger force at one end of the distal edge nearthe above-described other end wall than the other end of the same, andit is likely that the one end of the distal edge of the vane will becomeworn or broken.

SUMMARY OF THE INVENTION

An object of the present invention is to solve the above-describedproblem.

The present invention provides a vane air motor comprising a motorhousing having a cylindrical wall with a circular cylindrical innerperipheral surface and first and second end walls attached to theopposite ends, respectively, of the cylindrical wall, to thereby definea rotor chamber in the motor housing. The vane air motor furthercomprises a rotor provided in the motor housing to extend along an axisof rotation parallel to and spaced from the center axis of thecylindrical inner peripheral surface. The rotor has an output shaftportion extending through the second end wall and a support shaftportion extending into the first end wall. Further, the vane air motorcomprises vanes fitted to the rotor, first and second radial bearingsattached to the first and second end walls, respectively, to rotatablysupport the support shaft portion and the output shaft portion,respectively, and a casing contiguously joined to the motor housing toform a compressed air supply chamber together with the first end wall tosupply compressed air into the rotor chamber through an air supply holeformed in the first end wall. The first end wall has an end wall portionhaving an inner end surface abutting against an end surface of thecylindrical wall to define the rotor chamber together with thecylindrical inner peripheral surface of the cylindrical wall and anouter end surface opposite to the inner end surface in the axialdirection of the rotor. The end wall portion further has a circularcylindrical hole extending through the first end wall in the axialdirection of the rotor to receive the support shaft portion of the rotortherethrough. The first end wall further has a circular cylindrical wallportion extending from the outer end surface into the compressed airsupply chamber opposite to the rotor chamber to define a bearing-housingrecess housing the first radial bearing. The cylindrical wall portionhas an inner peripheral surface to which an outer peripheral surface ofan outer race of the first radial bearing is fitted and secured. Thefirst radial bearing comprises the outer race, an inner race fitted andsecured to an outer peripheral surface of the support shaft portion incoaxial relation to the outer race, and a plurality of rolling membersprovided between the outer race and the inner race. The first end wallhas a communication groove extending from an end surface of thecylindrical wall portion to the outer end surface of the end wallportion along the inner peripheral surface of the cylindrical wallportion.

In this vane air motor, a communication groove is provided to extendfrom an end surface of the cylindrical wall portion to the outer endsurface of the end wall portion along the inner peripheral surface ofthe cylindrical wall portion. Therefore, the air pressure in thecompressed air supply chamber is transmitted as far as the side of theradial bearing closer to the rotor chamber through the communicationgroove, so that a substantially uniform air pressure acts on both thefront and rear of the radial bearing (i.e., both sides of the radialbearing that are closer to the rotor chamber and the compressed airsupply chamber, respectively), thereby making it possible to prevent theabove-described leakage of grease from the radial bearing into the rotorchamber. Accordingly, it is possible to prevent the above-describedproblem that grease entering the rotor chamber adheres to the endportions of the vanes and causes the vanes to be inclined, resulting inthat only one end of the vane distal edge slides against the cylindricalwall surface of the rotor chamber and is eventually worn excessively orbroken.

Specifically, the outer end surface of the end wall portion may have acommunication recess communicating with the communication groove. Thecommunication recess is facing the radial bearing. More specifically,the communication recess may have an annular recess formed on the outerend surface of the end wall portion to extend circumferentially alongthe outer end surface radially outward of the cylindrical hole, and aradial recess formed on the outer end surface to extend radially fromthe annular recess to communicate with the communication groove. Thepurpose of this structure is to surely transmit the air pressure to theside of the radial bearing closer to the rotor chamber.

The vane air motor according to the present invention may comprise, inaddition to the above-described constituent elements, a governor havinga shaft-shaped rotating member secured to an end of the support shaftportion in coaxial relation thereto to rotate together with the supportshaft portion. When the shaft-shaped rotating member is rotated at anumber of revolutions greater than a predetermined one, the governorlimits an air supply flow path provided in the casing to supplycompressed air into the compressed air supply chamber to suppress thenumber of revolutions of the rotor. The shaft-shaped rotating member ofthe governor may have a flange extending radially of the shaft-shapedrotating member. The flange has an annular surface placed in closeproximity to an end surface of the outer race remote from the rotorchamber. With this structure, when the shaft-shaped rotating member ofthe governor rotates in response to the rotation of the rotor, theflange rotates in close proximity to the outer race. Therefore, it ispossible to prevent the air pressure of compressed air in the compressedair supply chamber from acting directly between the inner and outerraces of the radial bearing, and hence possible to reduce theabove-described leakage of grease.

Further, in the present invention, the end wall portion of the first endwall may have a radial hole extending through the end wall portionradially outward from the wall surface of the cylindrical hole andopening on the outer peripheral surface of the end wall portion tocommunicate with the atmosphere. With this structure, even if greaseleaks from the radial bearing toward the rotor chamber, the grease canbe discharged to the outside before reaching the rotor chamber.

An embodiment of the vane air motor according to the present inventionwill be explained below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional side view of a vane air motoraccording to the present invention.

FIG. 2 is a sectional side view of a first end wall defining a rotorchamber of the vane air motor shown in FIG. 1.

FIG. 3 is an end view of the first end wall shown in FIG. 2.

FIG. 4 is an enlarged sectional side view of the first end wall having aradial bearing installed therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a pneumatic grinder (polishing machine) 12 having a vaneair motor 10 according to the present invention.

The vane air motor 10 has a motor housing 20 having a cylindrical wall14 with a circular cylindrical inner peripheral surface and first andsecond end walls 16 and 18 provided at the opposite ends, respectively,of the cylindrical wall 14. The motor housing 20 has a rotor chamber 19formed therein. The vane air motor 10 further has a rotor 22eccentrically provided in the rotor chamber 19, a plurality of vanes 24fitted to the rotor 22, and a support shaft portion 28 and an outputshaft portion 26 that extend from the opposite ends of the rotor 22along the axis of rotation of the rotor 22 and that are supported by thefirst and second end walls 16 and 18, respectively. The vane air motor10 has a governor 30 attached to an end of the support shaft portion 28.The output shaft portion 26 is drivably connected to a rotating shaft 36of a disk-shaped abrasive member 32 through a bevel gear 34.

The rotating shaft 36, the vane air motor 10 and the governor 30 arehoused in a casing 38 of the pneumatic grinder 12. The casing 38comprises a plurality of casing parts 38-1 to 38-3. The casing part 38-3receives compressed air through a hose 40 connected to an air pump (notshown). The received compressed air is supplied into a compressed airsupply chamber 44 through a communicating hole 42 extending through thecasing part 38-3. The compressed air supply chamber 44 is formed aroundthe governor 30 by the casing part 38-3 and the first end wall 16. Thecompressed air is further supplied into the rotor chamber 19 through airsupply holes 46 and 48 provided at an upper position (as seen in thefigure) of the first end wall 16 and the cylindrical wall 14,respectively, to act on the vanes 24, thereby causing the rotor 20 torotate, and thus rotationally driving the abrasive member 32. Thecompressed air having acted on the vanes 24 is discharged into theatmosphere through exhaust holes 49.

The first end wall 16 is, as shown clearly in FIG. 4, provided with acircular cylindrical hole 60 communicating with the rotor chamber 19 andreceiving the support shaft portion 28 therethrough and abearing-housing recess 62 formed contiguous with the cylindrical hole 60at the side of the first end wall 16 remote from the rotor chamber 19. Aradial bearing 50 is provided in the bearing-housing recess 62. Theradial bearing 50 has an inner race 52 secured around the support shaftportion 28, an outer race 54 secured in the bearing-housing recess 62 ata position radially outward of the inner race 52, and bearing balls 56provided between the inner race 52 and the outer race 54. The radialbearing 50 rotatably supports the support shaft portion 28. Similarly,the second end wall 18 has a circular cylindrical hole 64 receiving theoutput shaft portion 26 therethrough, a bearing-housing recess 66, and aradial bearing 68.

The governor 30 has a shaft-shaped rotating member 70 coaxially securedto the end of the support shaft portion 28, a sleeve 72 slidablyprovided around the shaft-shaped rotating member 70, a pin 74 providedto extend diametrically through the shaft-shaped rotating member 70, acoil spring 76 provided between the pin 74 and the sleeve 72 to urge thesleeve 72 leftward as seen in the figure, and a ball 78 housed in aradial hole provided in the shaft-shaped rotating member 70. The ball 78is engaged with a tapered surface provided on the sleeve 72 and pressedradially by the urging force of the coil spring 76. When the rotor 20 isrotated at a number of revolutions greater than a predetermined one,together with the shaft-shaped rotating member 70, the ball 78 movesradially outward by centrifugal force, thus urging the tapered surfaceof the sleeve 72 to be displaced rightward as seen in the figure. Aconed disk spring 80 is provided at a position adjacent to a right-endsurface of the shaft-shaped rotating member 70 so as to extend acrossthe compressed air supply chamber 44 near the right end of the latter.The coned disk spring 80 has an air inlet hole 82 formed in the centerthereof to introduce compressed air passed through the communicatinghole 42 of the casing part 38-3 into the compressed air supply chamber44. When the sleeve 72 is displaced rightward as stated above, thesleeve 72 closes the air inlet hole 82 of the coned disk spring 80 tosuppress the supply of compressed air into the rotor chamber 19, therebysuppressing the rotation of the rotor 22. The shaft-shaped rotatingmember 70 of the governor 30 is provided with a flange 86 extendingradially of the rotating member 70. A surface of the flange 86 thatfaces the radial bearing 50 is placed in close proximity to an endsurface of the outer race 54 of the radial bearing 50 so that thepressure of compressed air in the compressed air supply chamber 44 actson the inside of the radial bearing 50 after it has been reduced,thereby suppressing grease in the radial bearing 50 from being pushedout toward the rotor chamber 19.

In the present invention, the following means is further provided toprevent grease in the radial bearing 50 from being pushed out into therotor chamber 19 by the effect of compressed air in the compressed airsupply chamber 44.

That is, as shown in FIGS. 2 to 4, the first end wall 16 has an end wallportion 16-3 having an inner end surface 16-1 abutting against the endsurface of the cylindrical wall 14 to define the rotor chamber 19together with the cylindrical inner peripheral surface of thecylindrical wall 14. The end wall portion 16-3 further has an outer endsurface 16-2 opposite to the inner end surface 16-1. Further, the firstend wall 16 has a circular cylindrical wall portion 16-4 extendingaxially from the end wall portion 16-3 to define the bearing-housingrecess 62. The first end wall 16 has a pair of communication grooves16-5 extending from the end surface of the cylindrical wall portion 16-4to the outer end surface 16-2 of the end wall portion 16-3 along theinner peripheral surface of the cylindrical wall portion 16-4. Thecommunication grooves 16-5 allow the air pressure in the compressed airsupply chamber 44 to be transmitted to the side of the radial bearing 50closer to the rotor chamber 19. Further, in the present invention, thefirst end wall 16 has an annular recess 16-6 and a pair of radialrecesses 16-7 on the outer end surface 16-2 of the end wall portion16-3. The annular recess 16-6 is formed around the cylindrical hole 60.The radial recesses 16-7 extend radially from the annular recess 16-6 tocommunicate with the communication grooves 16-5, respectively.

With the above-described structure, the air pressure in the compressedair supply chamber 44 is applied on both the front and rear of theradial bearing 50 (i.e. both sides of the radial bearing 50 that arecloser to the rotor chamber 19 and the compressed air supply chamber 44,respectively), thereby suppressing grease from being pushed out of theradial bearing 50 toward the rotor chamber 19.

Further, in the present invention, the end wall portion 16-3 of thefirst end wall 16 is provided with a radial hole 84 extending radiallyfrom the cylindrical hole 60 and opening on the outer peripheral surfaceof the end wall portion 16-3, so that grease that may be pushed outslightly from the radial bearing 50 flows out through the radial hole 84to the outside of the cylindrical wall 14 having the rotor chamber 19.

The vane air motor 10 according to the present invention, which has theabove-described structure, will make it possible to prevent leakage ofgrease from the radial bearing into the rotor chamber, which has beenexperienced with the conventional vane air motor. Further, in the vaneair motor, a flange is provided on the shaft-shaped rotating member ofthe governor, and an annular surface of the flange is placed in closeproximity to the end surface of the outer race. Because the annularsurface rotates at a high speed relative to the end surface of the outerrace, it forms a large flow path resistance with respect to a flow paththrough which the compressed air in the compressed air supply chamberformed around the governor passes to reach the radial bearing throughthe area between the annular surface and the end surface, wherebysuppress grease in the radial bearing is suppressed from being pushedout into the rotor chamber by the compressed air. Accordingly, it ispossible to prevent the problem that grease entering the rotor chamberadheres to the end portions of the vanes and causes the vanes to beinclined, resulting in that only one end of the vane distal edge slidesagainst the cylindrical wall surface of the rotor chamber and iseventually worn excessively or broken.

What is claimed is:
 1. A vane air motor comprising: a motor housingcomprising a cylindrical wall with a circular cylindrical innerperipheral surface, and first and second end walls that define oppositeends of the cylindrical wall, respectively, such that the circularcylindrical inner peripheral surface and the first and second end wallsdefine a rotor chamber in the motor housing; a rotor provided in themotor housing for rotation around an axis of rotation extending parallelto and spaced from a center axis of the circular cylindrical innerperipheral surface, the rotor having an output shaft portion extendingthrough the second end wall and a support shaft portion extending intothe first end wall; first and second radial bearings that are attachedto the first end wall and the second end wall, respectively, androtatably support the support shaft portion and the output shaftportion, respectively; and a casing joined to the motor housing to forma compressed air supply chamber together with the first end wall, thefirst end wall being formed with an air supply hole through whichcompressed air is supplied into the rotor chamber; the first end wallcomprising: an end wall portion having an inner end surface abuttingagainst an end surface of the cylindrical wall to define the rotorchamber, together with the circular cylindrical inner peripheral surfaceof the cylindrical wall, and an outer end surface located axiallyopposite to the inner end surface, the end wall portion further having acircular cylindrical hole which extends through the first end wall inthe axial direction of the rotor and receives the support shaft portionof the rotor so as to allow the support shaft portion to rotate in thecircular cylindrical hole; and a circular cylindrical wall portionextending opposite to the rotor chamber from the outer end surface intothe compressed air supply chamber to define a bearing-housing recesswhich houses the first radial bearing; the first end wall being formedwith a communication groove communicating with the compressed air supplychamber and extending to the outer end surface of the end wall portion,the outer end surface of the end wall portion being formed with acommunication recess forming an air passage configured in a loop aroundthe circular cylindrical hole which at least partially faces and thuscommunicates with a front end of the first radial bearing opposite to arear end thereof facing the compressed air supply chamber, thecommunication recess and the communication groove being in communicationwith each other and constituting an isolated channel to substantiallyuniformly pressurize the front and rear ends of the first radial bearingin order to prevent leaking of grease from the first radial bearing. 2.The vane air motor of claim 1, wherein the communication recesscomprises an annular recess formed in the outer end surface of the endwall portion around the cylindrical hole, and a radial recess formed inthe outer end surface to extend radially from the annular recess tocommunicate with the communication groove.
 3. The vane air motor ofclaim 1, further comprising: a governor having a shaft-shaped rotatingmember secured to an end of the support shaft portion coaxially with thesupport shaft portion so as to rotate together with the support shaftportion, wherein, when the shaft-shaped rotating member rotates fasterthan a predetermined speed, the governor limits an air supply ofcompressed air to the air supply hole of the motor housing to lower arotational speed of the rotor; the shaft-shaped rotating member of thegovernor having a flange extending radially of the shaft-shaped rotatingmember, the flange having an annular surface placed in close proximityto the other axial end of the first radial bearing.
 4. The vane airmotor of claim 1, wherein the end wall portion of the first end wall hasa radial hole extending through the end wall portion radially outwardfrom a wall surface of the circular cylindrical hole and opening on anouter peripheral surface of the end wall portion to communicate withatmosphere.